Folding knife



FIG. 1 is a left side-elevational view of the folding knife, showing my new design;

FIG. 2 is a right side-elevational view of the folding knife;

FIG. 3 is a left side-elevational view of the folding knife; and,

FIG. 4 is a top view of the folding knife. 

I claim the ornamental design for the folding knife, as shown and described. 